Pneumatic valves are one of many components of a system that controls the flow of a fluid through a system. Pneumatic valves are control devices powered by pressurized fluid, normally air. In many circumstances, pneumatic pressure is supplied to the driving, or actuating, portion of the valve from a pressure source. The driving portion of the valve transforms pneumatic pressure into mechanical power for operating or actuating a control mechanism in a supply line, duct, or pipe. The control mechanism may be an isolation valve having only two positions, open and closed, where the open position allows flow to pass and the closed position stops flow. The control mechanism may also be a control valve that is capable of modulating flow of the fluid it is controlling. For example, the control valve may allow fluid to pass in increments of one percent from zero percent to one hundred percent, or any desired command increment.
To control the supply of fluid into the driving portion of a pneumatic valve, a controlling device is often used. The controlling device regulates flow of the fluid into the driving portion of the pneumatic actuator using nozzles or control orifices that are regulated. One example of a controlling device is a torque motor, which uses an electromagnetic motor to control the opening and closing of nozzles to selectively provide air to the driving portion of a pneumatic actuator.